1. Field of the Invention
The present invention generally relates to a power supply system for portable electronic devices provided with rechargeable batteries, and more particularly, to a system for charging a rechargeable battery in a portable computer.
2. Related Art
Rechargeable batteries are commonly used to supply power to portable electronic devices, such as personal computers, wordprocessors, a variety of portable handsets and so on when conventional power outlets are not available. An AC (alternating current) adapter is also typically provided to power a portable device when the user does have access to a power outlet. The AC adapter further provides power to a battery charging circuit, which recharges the batteries, of the portable device.
When a rechargeable battery is used as a power supply system for portable personal computers as disclosed, for example, in U.S. Pat. No. 5,561,361 for Computer Power Supply And Battery Recharging System issued to Sengupta et al., the battery may be charged by the battery charger in two different charging modes, that is, a run and charging mode and a run or charging mode. During the run and charging mode, the battery is charged regardless whether the computer is operating or not, and as a result, the charging operation may be difficult to control. In contrast to the run and charging mode, the run or charging mode allows the battery to be charged selectively depending upon whether or not the computer is operating.
Generally, charging operations of such a battery may be classified into four modes, that is, a fast or rapid charging, a quick charging, a standard charging and a trickle charging, in relation to the charging capacities or charging current of the battery. In the fast charge mode, a relatively large charging current (e.g., about 2 amperes or so) is supplied to a battery over a relatively short period of time (e.g., one or two hours). In the quick charge mode, a relatively large charging current (e.g., about 1 ampere to high hundreds of milliamperes or so) is supplied to the battery over a relatively short period of time (e.g., four to six hours). In the standard charge mode, a relatively small charging current (e.g., about low hundreds of milliamperes or so) is supplied to the battery over a relatively long period of time (e.g. eight to ten hours). In the trickle charge mode, the battery charging circuit provides a relatively even smaller constant current (e.g., about 100 milliamperes or so) to the battery without interruption. In this mode, the battery may not be charged but its power loss due to natural discharge is compensated for. During all the charging operations, the charge level of the battery is monitored so that, when the battery reaches its maximum charge level, the charging operation is terminated in order to prevent overcharging and damage of the battery. Exemplars of contemporary battery chargers are disclosed in U.S. Pat. Nos. 4,843,299 and 5,049,804 for Universal Battery Charging System issued to Hutchings, U.S. Pat. No. 5,168,205 for Method And Apparatus For Charging A Battery In High Amp And Automatic Charging Modes issued to Kan et al., U.S. Pat. No. 5,175,485 for Apparatus For Controlling Charging Of A Storage Battery issued to Joo, U.S. Pat. No. 5,241,259 for Method and Apparatus For Rapidly Charging A Battery At High Temperature issued to Patino et al., U.S. Pat. No. 5,411,816 for Method And Apparatus For Determining Battery Characteristics issued to Patino, U.S. Pat. No. 5,479,083 for Non-Dissipative Battery Charger Equalizer issued to Brainard, U.S. Pat. No. 5,541,492 for Method For Charging A Multiple Voltage Electrochemical Cell issued to Fernandez et al., U.S. Pat. No. 5,592,069 for Battery Charger issued to Dias et al., U.S. Pat. No. 5,637,981 for Method For Charging A Secondary Battery And Charge Used Therefor Using Constant Current And Constant Voltage issued to Nagai et al., and the co-pending Korean application Ser. No. 96-45546 filed by the present applicant.
The following additional patents each disclose features in common with the present invention: U.S. Pat. No. 5,465,039 to Power Supply For Electronic Device, And Electronic Device System issued to Narita et al., U.S. Pat. No. 5,625,275 for Power Supply Which Provides A Variable Charging Current To A Battery In A Portable Computer System issued to Tanikawa et al., U.S. Pat. No. 5,481,175 for System And Method For Charging Auxiliary Batteries issued to Qualich et al., U.S. Pat. No. 5,462,029 for Constant Current Battery Charger With Auxiliary Output For Portable Apparatus issued to Seragnoli, U.S. Pat. No. 5,541,490 for Computer Power Supply System, issued to Sengupta et al., U.S. Pat. No. 5,568,038 for Portable Electric Equipment And Rechargeable Built-In Batteries issued to Tatsumi, U.S. Pat. No. 5,382,893 for Maximum Power Regulated Battery Charger issued to Dehnel, and U.S. Pat. No. 5,150,031 for Battery Charging System issued to James et al.